Electric conductor



(No Model.)

' T. A. EDISON.

ELECTRIC CONDUCTOR.

No. 470,924. Patented Mar. 15, 1892.

ES: 1 \/E 0:

W 7 f g UNITED STATES PATENT OFFICE.

THOMAS A. EDISON, OF LLEVVELLYN PARK, NEW JERSEY.

ELECTRIC CONDUCTOR.

SPECIFICATION forming part of Letters Patent No. 470,924, dated March 15, 1892.

Application filed September 30, 1887. Serial No. 251,093. (No model.)

To all whom it may concern: Be it known that I, THOMAS A. EDISON, o Llewellyn Park, in the county of Essex and State of New Jersey, have invented a certain new and useful Improvement in Electrical Conductors, (Case No. 732,) of which the following is a specification.

The object of my invention is to eifectively insulate wire, so that it will be waterproof and capable of being used in moist places and even under water without detriment to its insulating qualities, and also fire-proof, so that if by accident the wire becomes red-hot the insulating-covering will not be set on fire and burned, but only oxidation Will result, which will leave the wire pyro-insulated.

The main feature of the invention is the use as an insulating-covering of a mixture of rubber with an infusible material in the form of a powder.

I prefer to employ crude gum rubber, which I soften or partially dissolve by a suitable solventsuch as benzole-and then mix in a suitable mixing or kneading mill with about twice the quantity of the infusible powder, such as kaolin, chalk, carbonate of zinc, or phosphate of lime. The proportions of these substances will vary with the use to which the wire is to be put. They must be such that the covering, when placed upon the wire, will be flexible, water-proof, and a good insulator, and such that when the wire is heated the covering will not burst into a flame at any temperature up to the melting-point of the wire. lVhile pure rubber is an almost perfect insulator, it is so inflammable when used alone or in conjunction with cotton or other fabric that it cannot be safely used in electric-light wiring. In my in vention the infusible substance mixed with the rubber serves to prevent the flame, and a very considerable quantity thereof may be used without lowering the insulating and water-proof qualities too much for ordinary use. If the wire is to be used in situations where it requires to be bent sharply and so must be very flexible, or if it is to be used in very wet places, then the minimum amount of infusible material which will make the covering non inflammable must be used; also, the amount of rubber to the infusiblc material will vary, according to the character of the latter.

I prefer to employ for placing the covering upon the wire a press similar to the wellknown press for coating insulated wires with lead, except that only a small pressure is required, and the press therefore need not be one of great power.

The compound is placed in the press after being well mixed and kneaded to a doughy consistency.

Before passing the wire through the press I prefer to cover it with woven or braided cotton in the ordinary manner, which may be soaked with paraffine or other insulator. On the wire passing through the die of the machine, which is slightly larger than the wire, a very perfect and smooth coating of the compound of rubber and infusible material is pressed upon it. Afterward the volatile solventevaporates rapidly, and the coating hardens in a few seconds, so that the wire can be reeled up.

The completed wire is illustrated in the annexed drawings, Figure 1 being an elevation, and Fig. 2 a cross-section thereof.

A is the wire, B the cotton covering, and O the covering of the rubber compound.

What I claim isl. The combination of a wire, a fabric coverin g thereon, and an outer covering of a mixture of rubber and infusible material, substantially as set forth.

2. A conducting-wire having an insulatingcoating consisting of a quantity of rubber mixed with approximately twice as large a quantity of an infusible powder, whereby the coating is rendered practically non-combustible, substantially as described.

3. The conducting-wire having an insulating-coating consisting of a quantity of rubber mixed with a larger quantity of an infusible powder, whereby the coating is rendered practically non-combustible, substantially as described.

This specification signed and witnessed this 26th day of September, 1887.

THOS. A. EDISON.

Witnesses:

WILLIAM PELZER, E. G. ROWLAND. 

